U.S. patent number 5,599,510 [Application Number 08/447,434] was granted by the patent office on 1997-02-04 for catalytic wall reactors and use of catalytic wall reactors for methane coupling and hydrocarbon cracking reactions.
This patent grant is currently assigned to Amoco Corporation. Invention is credited to Narasimhan Calamur, George A. Huff, Jr., Mark P. Kaminsky, Michael J. Spangler.
United States Patent |
5,599,510 |
Kaminsky , et al. |
February 4, 1997 |
**Please see images for:
( Certificate of Correction ) ** |
Catalytic wall reactors and use of catalytic wall reactors for
methane coupling and hydrocarbon cracking reactions
Abstract
Dual-flow chemical reactor cores containing catalytic
heat-transfer walls comprising both a gas-impervious material and a
suitable catalyst which allows oxidative coupling of methane into
higher hydrocarbons, dual-flow reactors having these catalytic
heat-transfer walls to control and facilitate simultaneously
coupling of methane and cracking of hydrocarbon compounds in
separate gas streams, and chemical processes which combine coupling
of methane and cracking of hydrocarbon compounds to make olefins in
a dual-flow reactor having catalytic heat-transfer walls.
Inventors: |
Kaminsky; Mark P. (Winfield,
IL), Huff, Jr.; George A. (Naperville, IL), Calamur;
Narasimhan (Willowbrook, IL), Spangler; Michael J.
(Sandwich, IL) |
Assignee: |
Amoco Corporation (Chicago,
IL)
|
Family
ID: |
26805323 |
Appl.
No.: |
08/447,434 |
Filed: |
May 23, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
107912 |
Aug 17, 1993 |
|
|
|
|
815244 |
Dec 31, 1991 |
5254781 |
Oct 19, 1993 |
|
|
Current U.S.
Class: |
585/500; 585/602;
585/943; 585/910; 585/911; 422/651; 422/657; 422/659; 422/620 |
Current CPC
Class: |
B01J
8/009 (20130101); B01J 19/2485 (20130101); B01J
19/2475 (20130101); B01J 23/10 (20130101); B01J
23/14 (20130101); B01J 35/04 (20130101); C07C
2/84 (20130101); C07C 4/04 (20130101); C07C
4/06 (20130101); C07C 5/321 (20130101); C07C
5/48 (20130101); C10G 57/00 (20130101); B01J
15/005 (20130101); C07C 4/06 (20130101); C07C
11/02 (20130101); B01J 2219/00063 (20130101); B01J
2219/00117 (20130101); B01J 2219/00126 (20130101); B01J
2219/00155 (20130101); C07C 2521/02 (20130101); C07C
2521/06 (20130101); C07C 2523/02 (20130101); C07C
2523/08 (20130101); C07C 2523/10 (20130101); C07C
2523/14 (20130101); Y10S 585/911 (20130101); Y10S
585/91 (20130101); Y10S 585/943 (20130101) |
Current International
Class: |
B01J
15/00 (20060101); B01J 35/04 (20060101); B01J
35/00 (20060101); C07C 2/84 (20060101); C10G
57/00 (20060101); C07C 4/00 (20060101); C07C
4/04 (20060101); C07C 5/48 (20060101); C07C
5/00 (20060101); C07C 4/06 (20060101); C07C
5/32 (20060101); C07C 2/00 (20060101); B01J
19/24 (20060101); B01J 8/00 (20060101); B01J
23/14 (20060101); B01J 23/10 (20060101); C07C
002/00 () |
Field of
Search: |
;422/188,190,192,193,191,196,197,198,202,222
;585/500,602,910,911,943 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Smith et al., Chemical Engineering Science, vol. 30, pp. 221-222
(1975). .
Hatano et al., Inorganica Chimica Acta., vol. 146, pp. 243-247
(1988). .
Ungar et al., Applied Catalysts, vol. 42, pp. L1-L4 (1988). .
Zhang et al., J. Chem. Soc., Chem. Commun., pp. 473-475
(1989)..
|
Primary Examiner: Warden; Robert J.
Assistant Examiner: Carpenter; Robert
Attorney, Agent or Firm: Oliver; Wallace L. Jerome;
Frederick S.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of application Ser. No.
08/107,912 filed Aug. 17, 1993, which is a continuation-in-part of
application Ser. No. 07/815,244 filed Dec. 31, 1991, now U.S. Pat.
No. 5,254,781, issued Oct. 19, 1993, the specifications and claims
of which are incorporated by reference herein.
Claims
That which is claimed is:
1. A process to make olefins which comprises the steps of:
(A) providing a cross-flow chemical reactor fox combined coupling
of methane using an oxygen-affording gas and dehydrogenating of
saturated hydrocarbon compounds in separated reaction spaces, which
reactor comprises;
a vessel having an entrance port, an exit port, and a passageway
therebetween containing a stream of one or more gases flowing from
the entrance port to the exit port operable to define a direction
of stream flow, and
passageway therebetween containing a stream of one or more gases
flowing from the entrance port to the exit port operable to define
a direction of stream flow, and
at least one reactor core positioned within the vessel comprising
an array of tubes having an outer surface including a generally
flat entrance surface and a generally flat exit surface spaced
apart from and substantially parallel to the entrance surface, and
a plurality of tube channels therebetween containing one or more
gases flowing from the entrance surface to the exit surface
operable to define a direction of channel flow, wherein each
channel has a catalytic heat-transfer wall disposed between the
channel and a portion of the outer surface of the tubes contacting
the gas stream in the passageway, the catalytic heat-transfer wall
comprising a ceramic antifoulant coating, a gas-impervious material
comprising a high temperature metal or metallic alloy, and, on the
portion of the outer surface of the tubes contacting the gas stream
in the passageway, a suitable catalyst means for oxidative coupling
of methane into higher hydrocarbons, the reactor core further
comprising an entrance manifold means in flow communication with
channels at the entrance surface of at least one array and an exit
manifold means in flow communication with the same channels at one
or more exit surface and thereby in flow communication with
entrance manifold means, and
wherein the entrance port, the passageways, the outer surfaces of
the tubes, and the exit port form a first zone for introducing and
reacting at least one compound therein, and expelling a first gas
or gas mixture and wherein the entrance manifold means, the tube
channels and the exit manifold means form a second zone within the
dual-flow chemical reactor for introducing, reacting at least one
compound therein, and expelling a first gas or gas mixture and
wherein the entrance manifold means, the tube channels and the exit
manifold means form a second zone within the dual-flow chemical
reactor for introducing, reacting at least one compound therein,
and expelling a second gas or gas mixture;
(B) introducing a first feed stream which is essentially methane
and an oxygen-affording gas into the first zone, coupling the first
feed to produce a product containing C.sub.2 hydrocarbons and
effectively transferring heat evolved by coupling through the
catalytic heat-transfer wall into the second zone, and expelling a
residue of the first feed stream,
(C) introducing a second feed stream which contains predominantly
saturated hydrocarbons into the second zone, cracking at least one
of the saturated hydrocarbons using heat evolved by coupling from
the first zone to provide a majority of the heat required by the
cracking to form primarily an olefin-containing product, and
expelling a product-containing gas mixture,
(D) combining the C.sub.2 + containing portions of the effluents
from the first zone and the second zone and individually separating
the methane and at least the ethylene and propylene olefinic
hydrocarbon components thereof, and
(E) returning unreacted methane contained in the effluent of the
first zone together with methane contained in the effluent of the
second zone to the first feed stream.
2. The process of claim 1 wherein the hydrocarbons contained in the
second feed stream are thermally cracked in the presence of a
fluidized bed of particulate solids in the second zone.
3. The process of claim 1 wherein hydrocarbons contained in the
second feed stream are thermally cracked in the presence of steam,
and wherein the separating of the methane and at least the ethylene
and propylene components is carried out cryogenically using
hydrocarbons and nitrogen as refrigerants.
4. The process of claim 3 wherein the oxygen-affording gas is
essentially oxygen separated from air by liquefaction and
fractionation to obtain an essentially oxygen fraction and an
essentially nitrogen fraction, and wherein the nitrogen fraction is
used to liquefy one or more methane, ethylene and propylene, each
under moderate pressure, to provide one or more cryogenic liquids
used to effect the cryogenic separation of the olefinic hydrocarbon
components.
5. The process of claim 1 wherein the gas-impervious material
comprises nickel or a metallic alloy thereof.
6. The process of claim 5 wherein hydrocarbons contained in the
second feed stream are thermally cracked, and wherein the
separating the methane and at least the ethylene and propylene
components thereof is carried out cryogenically using hydrocarbons
and nitrogen as refrigerants.
7. The process of claim 6 wherein said oxygen-affording gas is
essentially oxygen which is separated from air by liquefaction and
fractionation to obtain an essentially oxygen fraction and an
essentially nitrogen fraction, and where the nitrogen fraction is
used to liquefy one or more of methane, ethylene and propylene,
each under moderate pressure, to provide one or more cryogenic
liquids used to effect the cryogenic separation of said olefinic
hydrocarbon components.
8. A process to make olefins which combines cracking of a
hydrocarbon feedstock with coupling of methane, the process
comprising the steps of:
providing a combined process reactor suitable for coupling of
methane using an oxygen-affording gas and dehydrogenating of
saturated hydrocarbon compounds in separated reaction spaces, which
reactor comprises;
a first reaction space and
a second reaction space separated from the first reaction space by
catalytic thermally conducting tube walls comprising a suitable
catalyst means for oxidative coupling of methane into higher
hydrocarbons;
coupling in the first reaction space of a first feed stream which
is essentially methane using an oxygen-affording gas to produce a
product containing C.sub.2 hydrocarbons, and transferring heat
evolved by coupling through the catalytic heat-transfer wall into
the second reaction space;
hydrocarbon cracking in the second reaction space of a second feed
stream which contains predominantly saturated hydrocarbons to form
primarily an olefin-containing product;
effectively using the heat evolved by coupling in the first space
which is transferred through the catalytic heat-transfer wall to
provide a majority of the heat required by the cracking without
mixing hot effluent of the first reaction space into the second
reaction space;
combining the C.sub.2 + containing portions of the effluents from
the first reaction space and the second reaction space, and
individually separating the methane and at least the ethylene and
propylene olefinic hydrocarbon components thereof; and
returning unreacted methane contained in the effluent of the first
reaction space together with methane contained in the effluent of
the second reaction space to the first reaction space.
9. The process to make olefins according to claim 8 wherein the
catalytic thermally conducting tube walls comprise a ceramic
antifoulant coating, the gas-impervious material comprising a high
temperature metal or metallic ahoy, and the suitable catalyst means
for oxidative coupling of methane into higher hydrocarbons is
adhered to the walls in the form of a skin on the reactor tube to
facilitate transport of heat across the reactor wall whereby a
majority of the heat required in the endothermic cracking process
is supplied by the heat evolved in the methane coupling.
10. The process to make olefins according to claim 9 wherein the
catalyst means for oxidative coupling of methane comprises at least
one oxidized metal selected from the group consisting of scandium,
yttrium, lanthanum, magnesium, calcium, strontium, and barium.
11. The process to make olefins according to claim 9 wherein the
gas-impervious material comprises nickel or a metallic alloy
thereof.
12. The process to make olefins according to claim 9 wherein the
catalyst means for oxidative coupling of methane comprises a
combination of at least one oxidized Group IIIA metal and at least
one oxidized Group IIA metal.
13. The process to make olefins according to claim 9 wherein the
oxygen-affording gas is essentially oxygen which is separated from
air by liquefaction and fractionation to obtain an essentially
oxygen fraction and an essentially nitrogen fraction, and where the
nitrogen fraction is used to liquefy one or more of methane,
ethylene and propylene, each under moderate pressure, to provide
one or more cryogenic liquids used to effect the cryogenic
separation of the olefinic hydrocarbon components, and wherein
hydrocarbons contained in the second feed stream are thermally
cracked.
Description
TECHNICAL FIELD
This invention relates to chemical reactors useful to control
simultaneously partial oxidation and pyrolysis reactions of
different organic compounds to added-value products. In particular,
this invention relates to dual-flow chemical reactors containing
catalytic heat-transfer walls which have both gas-impervious
materials and suitable catalysts allowing oxidative coupling of
methane into higher hydrocarbons, and chemical processes using
dual-flow reactors having such catalytic heat-transfer walls to
control and facilitate transport of heat from methane coupling
reactions in a methane-containing gas stream to cracking reactions
of organic compounds in separate gas stream. These dual-flow
reactors comprise either an array of tubes containing channels for
flow of one gas stream positioned in another gas stream flow or a
core containing channels for separated flow of a methane-containing
gas stream and flow of organic compounds in another gas stream.
Each channel has a portion of thermally conductive wall disposed
between at least two different gas streams comprising a
gas-impervious material and suitable catalyst for oxidative
coupling of methane into higher hydrocarbons.
The invention includes reactors comprising first and second zones
separated by catalytic heat-transfer walls which have both
gas-impervious materials and suitable catalysts allowing oxidative
coupling of methane into higher hydrocarbons. Preferred
gas-impervious materials comprise high temperature metal alloys
and/or non-metals materials including stainless steels, ceramics,
silicon carbide, and the like.
The invention also includes a process for making olefins using a
dual-flow reactor having catalytic heat-transfer wails to control
and facilitate transport of heat from methane coupling reactions in
a methane-containing gas stream to cracking reactions of organic
compounds in another gas stream. This process combines the thermal
and/or catalytic cracking of a hydrocarbon feed stock with the
coupling of methane and allows separation of an enhanced amount of
C.sub.2 + products, and more particularly, to a process for making
olefins in which a hydrocarbon feed is thermally cracked to form
olefins in parallel with the catalytic coupling of methane to form
largely C.sub.2 hydrocarbons using an oxygen-affording gas, the
methane coupling and cracking processes so arranged that the heat
produced in the exothermic coupling reaction is effectively
transferred to the endothermic cracking process, and in which the
refrigeration required to liquefy air to produce oxygen for the
methane coupling process is used to effect the cryogenic separation
of the products contained in the effluent from the cracking
process.
BACKGROUND OF INVENTION
It is well known that capacity of conventional reactors for
chemical conversions of commercial interest is often heat transfer
limited, because such chemical conversions are highly exothermic,
endothermic, and/or require severe thermal conditions of reaction.
For example, conventional fixed-bed and fluidized-bed catalytic
reactors for exothermic gas phase reactions in which a
catalytically active material is supported on or contained within
solid particles, typically, have large gas-solid thermal
resistance. In particular, one such technique is oxidative coupling
of methane which involves reacting methane with oxygen over
supported catalyst to produce higher hydrocarbons, principally
ethane and ethylene, in fixed-bed and/or fluidized-bed catalytic
reactors.
The commercial production of olefins including importantly
ethylene, propylene and smaller amounts of butadiene and butylenes
is generally accomplished by the thermal cracking using steam of
ethane, propane or a hydrocarbon liquid ranging in boiling point
from light straight run gasoline through gas oil. In a typical
ethylene plant the cracking furnaces represent about 25% of the
cost of the unit while the compression, heating, dehydration,
recovery and refrigeration sections represent the remaining about
75% of the total. This endothermic process is carried out in large
pyrolysis furnaces with the expenditure of large quantities of heat
which is provided in part by burning the methane produced in the
cracking process. After cracking, the reactor effluent is put
through a series of separation steps involving cryogenic separation
of products such as ethylene and propylene. The total energy
requirements for the process are thus very large and ways to reduce
it are of substantial commercial interest. In addition, it is of
interest to reduce the amount of methane produced in the cracking
process, or to utilize it other than for its fuel value.
More recently, because of the supply side pressure to find
non-petroleum sources for industrial chemicals and the
environmental need to reduce methane flaring from producing oil
wells, natural gas, a source which is relatively abundant in the
United States and other locations elsewhere in the world, has been
investigated as a source of hydrocarbons and oxygenates. Various
methods to convert the methane in natural gas to hydrocarbons have
been suggested and some commercialized. Projects in New Zealand and
at Sasol in South Africa are examples in which methane is converted
to useful products. In New Zealand, methane is converted to a
methanol and then to hydrocarbons, and in Sasol, methane is
converted to synthesis gas and then to other products. Another such
project is located in Malaysia.
Direct conversion of methane to major industrial intermediates such
as ethylene and propylene has been the subject of much research in
the past 10 years. While a number of catalysts and processes have
been suggested for the conversion none, has yet been
commercialized. One process which has been intensely researched is
the high temperature methane coupling process using an
oxygen-affording gas and a solid, metal oxide catalyst to form
largely ethane and ethylene. Carbon dioxide formation which is
favored thermodynamically is an undesired product in methane
coupling as its formation uses carbon which is not readily
available to form the desired hydrocarbons.
Pyrolysis processes are known which involve conversion of methane
to higher molecular weight hydrocarbons at high temeratures, in
excess of about 1200.degree. C. These processes are, however energy
intensive and have not been developed to the degree where high
yields are obtained even with use of catalysts.
U.S. Pat. No. 4,507,517 and U.K. Patent Application GB 2,148,935A
have taught catalytic processes for converting methane to C.sub.2 +
hydrocarbons, particularly hydrocarbons rich in ethylene and/or
benzene, at temperatures greater than 1000.degree. C. and gas
hourly space velocities in excess of 3200 hr.sup.-1. The U.S.
patent used a boron containing catalyst. While the U.K. application
disclosed a process which used a catalyst containing a metal
compound of Groups IA, IIA, IIIA, IVB or Actinide Series of
elements.
Catalytic oxidative coupling of methane at atmospheric pressure and
temperatures in a range of from about 500.degree. C. to about
1000.degree. C. has been investigated by G. E. Keller and M. M.
Bhasin. These researchers reported synthesis of ethylene via
oxidative coupling of methane over a wide variety of metal oxides
supported on an alpha alumina structure in Journal of Catalysis,
73, pages 9 to 19 (1982). They teach use of single component oxide
catalysts that exhibited methane conversion to higher order
hydrocarbons at rates no greater than 4%. The process used by
Keller and Bhasin to oxidize methane was cyclic, varying the feed
composition between methane, nitrogen and air (oxygen) to obtain
higher selectivities.
U.S. Pat. Nos. 4,443,644; 4,443,645; 4,443,646; 4,443,647;
4,443,648,; 4,443,649; and 4,523,049 also disclose methods for
converting methane to higher molecular weight hydrocarbons at
temperatures in a range of about 500.degree. C. to about
1000.degree. C.
Low temperature pyrolysis of hydrocarbon feed stocks to higher
molecular weight hydrocarbons at temperature in a range of about
250.degree. C. to about 500.degree. C. is reported in U.S. Pat.
Nos. 4,433,192; 4,497,970; and 4,513,164. Processes described in
these patents used heterogeneous systems and solid acid catalysts.
In addition to the solid acid catalysts, the reaction mixtures
described in latter two patents included oxidizing agents. Among
the oxidizing agents disclosed are air, O2/O3 mixtures, S, Se,
SO.sub.3, N.sub.2 O, NO, NO.sub.3 F, and the like.
U.S. Pat. Nos. 4,172,810; 4,205,194; and 4,239,658 teach production
of hydrocarbons including ethylene, ethane, propane, and benzene in
the presence of a catalyst-reagent composition which comprises; (i)
nickel, or a Group VIII metal or a Group IB having atomic number of
45 or greater; (ii) a Group VIB; and (iii) a preselected Group IIA
metal; composted, for example, with a persisted, spinel-coated
refectory support. Feed streams used in processes disclosed in
these patents did not contain oxygen. Oxygen was avoided for the
purposes of avoiding formation of coke in the catalyst. Oxygen was
generated for reaction from the catalysts; thus periodic
regeneration of these catalysts was required.
U.S. Pat. No. 4,450,310 teaches production of olefins and hydrogen
from methane in the absence of oxygen and in the absence of water
at reaction temperatures of at least 500.degree. C. using catalyst
comprising mixed oxides of a first metal selected from the group
lithium, sodium, potassium, rubidium, cesium and mixtures thereof,
a second metal selected from the group beryllium, magnesium,
calcium, strontium, barium, and mixtures thereof, and optionally a
promoter metal selected from the group copper, rhenium, tungsten,
zirconium, rhodium, and mixtures thereof.
U.S. Pat. No. 4,560,821 discloses a continuous process for forming
hydrocarbons from a source of methane by contacting methane with
particles of catalyst wherein the particles circulate between two
physically separate zones; a methane contact zone and an oxygen
contact zone. In each zone the particles are maintained as
fluidized beds of the solid particles. Useful catalysts are said to
include reducible oxides of metals selected from the group Mn, Sn,
In, Ge, Pb, Sb and Bi.
In U.S. Pat. No. 4,926,001, Institut Francais du Petrole (IFP) has
taught a stem cracking process for thermal conversion of methane to
hydrocarbons of higher molecular weights based on use of a
multichannel system of ceramic material in which a methane feed
passes through a pyrolysis zone followed by a quenching zone in a
first set parallel rows of channels which are cooled by a cooling
fluid passing through a second set of parallel rows of adjacent
channels. Pyrolysis zone and following quenching zone are open to
flow of methane and/or hydrocarbons directly from one zone to the
another zone in the multichannel system described.
U.S. Pat. No. 5,012,028 discloses a continuous process for
converting a gaseous reactant containing methane or natural gas to
hydrocarbons wherein the gaseous reactant is contacted with an
oxidative coupling catalyst in an oxidative coupling reactor at a
reaction temperature in a range from 500.degree. C. to 1100.degree.
C. to form an intermediate product, predominately ethane; and
pyrolysis of an admixture of the intermediate product with a source
other C.sub.2 + gases in a pyrolysis reactor at a reaction
temperature in a range from 900.degree. C. to 1500.degree. C. to
form higher molecular weight hydrocarbon products. The total
effluent from the oxidative coupling reactor or zone flows directly
to the pyrolysis reactor or zone. Catalyst is supported on inert
solid particles which are in the forms of fixed bed, fluid bed,
spouted bed or monolith. External heat is, typically, applied to
the pyrolysis reactor to supplement the heat provided with effluent
from the oxidative coupling reactor.
Recently in U.S. Pat. No. 5,025,108, Institut Francais du Petrole
(IFP) has taught a process for producing olefins from natural gas
which involves pre-separation of the C.sub.2 + components from the
methane, catalytic oxidation of the methane to primarily ethane and
ethylene, and the return of the C.sub.2 + components to the
effluent side of the methane coupling reaction where the saturated
C.sub.2 + components are then cracked to olefins. The process is
said to effectively utilize the heat produced in the exothermic
methane coupling to carry out the endothermic cracking process. The
process has several drawbacks, however, including importantly the
mixing of the carbon oxides and water components produced by the
substantial amount of hydrocarbon burning in the methane coupling
process into the cracking process stream. Such components require
an expensive separation from the hydrocarbons downstream in the IFP
process.
More recently U.S. Pat. No. 5,118,898 has taught a process for
producing ethylene from a methane rich gas stream and an ethane
rich gas stream by (i) introducing the methane rich gas stream and
molecular oxygen into a lower zone of a fluidized bed of particles
which are catalytically active in promoting an exothermic oxidative
coupling reaction to product ethylene and other hydrocarbons, (ii)
subjecting the effluent from (i) to an endothermic pyrolysis
reaction in an upper zone of the same fluidized bed of catalytic
particles to produce further ethylene and other olefinically
unsaturated hydrocarbons. Use of a single fluidized bed has several
drawbacks, however, including importantly back mixing of the
catalytic particles and hydrocarbon components produced in the
upper into the lower zone of the fluidized bed containing molecular
oxygen. While circulation of the fluidized bed of particles within
the reactor is able to transfer exothermic heat from the oxidative
coupling zone to the pyrolysis zone of the fluidized bed, both of
the steps (i) and (ii) must occur at substantially the same
temperature.
SUMMARY OF INVENTION
In broad aspect, the invention is an apparatus using integrated
catalytic heat-transfer walls for simultaneously coupling of
methane and dehydrogenating of saturated hydrocarbon compounds in a
separate gas. The apparatus comprises either an array of tubes
containing channels for flow of one gas stream positioned in
another gas stream or a core containing channels for separate flow
of a first feed which is essentially methane and the
oxygen-affording gas and a second feed which contains predominantly
saturated hydrocarbons. Each channel has a catalytic heat-transfer
wall disposed between the channel and a portion of the outer
surface of the tube contacting the gas stem in the passageways, or
a common catalytic heat-transfer wall with adjacent core channels.
The catalytic heat-transfer wall comprising a gas-impervious
material and a suitable catalyst allowing oxidative coupling of
methane into higher hydrocarbons.
Using apparatus of the invention for simultaneously coupling of
methane and dehydrogenating of saturated hydrocarbon compounds in a
separate gas now provides a way to produce olefins in a process not
having many of the past disincentives. The process integrates the
production of the olefins by hydrocarbon cracking with the methane
coupling in a manner in which the individual processes
synergistically fit together. Realized objectives of the new
process are:
1. Thermal integration of the endothermic olefin cracking process
with the exothermic methane coupling process;
2. Thermal integration of the refrigeration processes for enriched
or purified oxygen production, olefins recovery, and optionally,
natural gas liquids processing;
3. High overall yield of olefins and other products with near
complete feed stock utilization; and
4. Substantial reduction of NO.sub.x as a result of process heat
being generated by the coupling of methane with oxygen rather than
the combustion of fuel with air.
Suitable catalysts allowing oxidative coupling of methane include
catalyst comprising at least one element selected from the group
consisting of Group IIA and Group IIIA of the periodic table of
elements, preferably, at least one oxidized metal selected from the
group consisting of magnesium, calcium, strontium, barium,
scandium, yttrium, lanthanum, and scandium. Preferred catalysts
comprise a combination of at least one oxidized Group IIIA metal,
and at least one oxidized Group IIA metal. More preferred are
catalysts which further comprises a cationic species of at least
one element selected from the group consisting of aluminum,
germanium, tin, and lead. Halides may also be present in useful
catalyst compositions.
In one aspect, the invention is a dual-flow chemical reactor for
simultaneous oxidative coupling of methane using an
oxygen-affording gas and cracking-dehydrogenating reactions of
organic compounds in a separate gas. In one embodiment of the
invention, the dual-flow chemical reactor comprises a vessel having
an entrance port, an exit port, and a passageway therebetween for
stream flow of one or more gases from the entrance port to the exit
port defining a direction of stream flow. Preferably, the direction
of stream flow and the direction of channel flow are substantially
transverse to one another. At least one reactor core, positioned
within the vessel, comprises an array of tubes having an outer
surface including a generally flat entrance surface and a generally
flat exit surface spaced apart from the entrance surface, and a
plurality of tube channels therebetween for flow of one or more
gases from the entrance surface to the exit surface operable to
define a direction of channel flow. Each channel has a catalytic
heat-transfer wall disposed between the channel and a portion of
the outer surface of the tubes contacting the gas stream in the
passageway. The reactor core further comprises an entrance manifold
means in flow communication with channels at the entrance surface
of at least one array and an exit manifold means in flow
communication with the same channels at one or more exit surface
and thereby in flow communication with entrance manifold means. The
vessel and the reactor core together form a first zone for
introducing, reacting at least one compound therein, and expelling
a first gas or gas mixture and wherein the entrance manifold means,
the tube channels and the exit manifold means form a second zone
within the dual-flow chemical reactor for introducing, reacting at
least one compound therein, and expelling a second gas or gas
mixture.
In another aspect, the invention is a dual-flow core for
simultaneous coupling of methane using an oxygen-affording gas and
dehydrogenating of saturated hydrocarbon compounds in separate gas
which comprises a ceramic core having a generally flat first
entrance surface, a generally flat first exit surface spaced apart
from and substantially parallel to the first entrance surface, and
a first plurality of core channels therebetween for flow of a first
feed which is essentially methane and the oxygen-affording gas from
the first entrance surface to the first exit surface operable to
define a first direction of channel flow. The ceramic core also
having a generally flat second entrance surface, a generally flat
second exit surface spaced apart from and substantially parallel to
the second entrance surface, and a second plurality of core
channels therebetween for flow of a second feed which contains
predominantly saturated hydrocarbons, from the second entrance
surface to the second exit surface operable to define a second
direction of channel flow. Each channel has a portion of channel
wall disposed between the oxygen-containing gas stream and the
other gas stream comprising a gas-impervious material and a
suitable catalyst allowing oxidative coupling of methane into
higher hydrocarbons.
In yet another aspect, the invention is a dual-flow chemical
reactor for simultaneous coupling of methane using an
oxygen-affording gas and dehydrogenating of saturated hydrocarbon
compounds in another gas which comprises at least one ceramic core
having a generally flat first entrance surface, a generally flat
first exit surface spaced apart from and substantially parallel to
the first entrance surface, and a first plurality of core channels
therebetween for flow of a first feed which is essentially methane
and the oxygen-affording gas from the first entrance surface to the
first exit surface operable to define a first direction of channel
flow. The ceramic core also having a generally flat second entrance
surface, a generally flat second exit surface spaced apart from and
substantially parallel to the second entrance surface, and a second
plurality of core channels therebetween for flow of a second feed
which contains predominantly saturated hydrocarbons, from the
second entrance surface to the second exit surface operable to
define a second direction of channel flow. Each channel has a
portion of channel wall disposed between the oxygen-containing gas
stream and the other gas stream comprising a gas-impervious
material and a suitable catalyst allowing oxidative coupling of
methane into higher hydrocarbons. The reactor further comprising a
first entrance manifold means in flow communication with first
plurality of core channels at the first entrance surface and a
first exit manifold means in flow communication with the same
channels at the first exit surface, thereby in flow communication
with first entrance manifold means, and a second entrance manifold
means in flow communication with second plurality of core channels
at the second entrance surface and a second exit manifold means in
flow communication with the same channels at the second exit
surface, thereby in flow communication with second entrance
manifold means. The first entrance manifold means, plurality of
core channels and exit manifold means together form a first zone
for introducing, reacting at least one compound therein and
expelling a first gas or gas mixture and the second entrance
manifold means, plurality of core channels and exit manifold means
together form a second zone for introducing, reacting at least one
compound therein and expelling a second gas or gas mixture.
In another aspect, the invention is a integrated chemical
conversion process to make olefins which combines coupling of
methane and cracking of hydrocarbon compounds in separate gas
streams which comprises the steps of
(A) providing at least one dual-flow chemical reactor described
above,
(B) introducing a first feed stream which is essentially methane
and an oxygen-affording gas into either the first or second zone,
coupling the first feed to produce a product containing C.sub.2
hydrocarbons and effectively transferring heat evolved by coupling
through the catalytic heat-transfer wall into the other zone, and
expelling a residue of the first feed stream,
(C) introducing a second feed stream which contains predominantly
saturated hydrocarbons into the other zone, cracking at least one
of the saturated hydrocarbons using heat evolved by coupling from
the first zone to provide a majority of the heat required by the
cracking to form primarily an olefin-containing product, and
expelling a product-containing gas mixture, and
(D) combining the C.sub.2 + containing portions of the effluents
from the first zone and the second zone and individually separating
the methane and at least the ethylene and propylene olefinic
hydrocarbon components thereof.
In preferred embodiment of a process according to the invention,
the process includes a step
(E) returning unreacted methane contained in the effluent of the
first zone together with methane contained in the effluent of the
second zone to the first feed stream.
In processes according to the invention, it is preferred to have
the catalytic coupling of methane reaction and the hydrocarbon
cracking reaction are separated by a thermally conductive catalytic
heat-transfer wall which is in good thermal contact with both of
these reactions.
In another preferred embodiment of a process according to the
invention, the hydrocarbons contained in the second feed stream are
thermally cracked in the presence of a fluidized bed of particulate
solids in the first zone, and/or wherein the coupling is
catalytic.
In another preferred embodiment of a process according to the
invention, the hydrocarbons contained in the second feed stream are
thermally cracked with or without the presence of steam, the
coupling is catalytic, and/or wherein separating methane and at
least the ethylene and propylene components thereof is carried out
cryogenically using hydrocarbons and nitrogen as refrigerants.
In still another preferred embodiment of a process according to the
invention, the oxygen-affording gas is essentially oxygen separated
from air by liquefaction and fractionation to obtain an essentially
oxygen fraction and an essentially nitrogen fraction, and wherein
the nitrogen fraction is used to liquefy one or more methane,
ethylene and propylene, each under moderate pressure, to provide
one or more cryogenic liquids used to effect the cryogenic
separation of the olefinic hydrocarbon components.
BRIEF DESCRIPTION OF THE DRAWINGS
The appended claims set forth those novel features which
characterize the present invention. The present invention itself,
as well as advantages thereof, may best be understood, however, by
reference to the following brief description of preferred
embodiments taken in conjunction with the annexed drawings, in
which:
FIG. 1 is an exploded perspective view of one embodiment of a
dual-flow reactor in accordance with the present invention;
FIG. 2 is a sectional view of the dual-flow reactor of FIG. 1;
FIG. 3 is an exploded perspective view of another embodiment of a
dual-flow reactor in accordance with the present invention; and
FIG. 4 is a sectional view of a dual-flow core in accordance with
the present invention.
FIG. 5 is a side view and cross-sectional view of yet another
embodiment of a dual-flow core in accordance with the present
invention.
BRIEF DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 illustrate a dual-flow reactor 10 having a reactor
core 11 containing an array of five tubes 14 which are positioned
across passageways 24 for flow of a gas stream. The reactor core 11
has opposite outer side walls 12 which are generally flat and
approximately 90.degree. from an entrance surface for flow through
the core and an opposite side exit surface spaced apart from and
substantially parallel with each other. The array of reactor tubes
together is approximately a rectangular parallelepiped shape. The
reactor core 11 has a plurality of tube channels 13 between the
entrance surface (not shown) of an entrance and exit surface 19
manifold tube sheet for flow of gases from entrance surface to
opposite exit surface and defining a direction of channel flow
which is rotated approximately 90.degree. from the entrance and
exit surfaces and is approximately 90.degree. from the direction of
stream flow through the core. Each channel 13 has a catalytic
heat-transfer wall disposed between the channel and a portion of
outer tube surface exposed to gas stream. Structures 15 and 21
adjacent opposite entrance and exit surfaces of the reactor core 11
define spaced entrance manifold (not shown) and opposite exit
manifold 20 that communicate with one another via channels 13
formed in the tubes. Further, structures 22 and 26 adjacent
opposite top and bottom outer surfaces of the reactor core 11
define spaced entrance and exit manifolds (not shown) that
communicate with one another via passageways 24 formed by spaces
between outer surfaces of the core tubes and wall structures 12. An
inlet line 33 in structure 15 is adapted to carry either an organic
compound in an oxygen-affording gas stream or another gas stream
containing reactants comprising one or more organic compounds to
the entrance manifold for flow through channels 13, and an outlet
line 35 in structure 21 is adapted to carry a residue of the
oxygen-affording gas stream or all remaining gas, unconsumed
reactants, and product-containing gas mixture from the exit
manifold. Likewise, inlet line 44 in structure 22 is adapted to
carry either an organic compound in an oxygen-affording gas stream
or another gas stream containing reactants comprising one or more
organic compounds to the entrance manifold for flow through
passageways 24, and an outlet line 46 in structure 26 is adapted to
carry a residue of the oxygen-containing gas stream or all
remaining gas, unconsumed reactants, and product-containing gas
mixture from the exit manifold. Passageways 24 and channels 13 are
disposed transverse to one another, so that the respective inlet
and outlet manifolds for an organic compound in an
oxygen-containing gas stream and for the another gas stream
containing reactants are located alternately adjacent one
another.
FIG. 2 illustrates an enlarged cross section of reactor core 11 for
dual-flow reactor 10 of FIG. 1. Channels 13, specifically shown for
a gas stream of an organic compound in an oxygen-affording gas, are
illustrated to extend in the plane of the viewing paper and are
formed by catalytic heat-transfer walls 51 comprising a
gas-impervious material 53 supporting a suitable catalyst 55 which
together form a thermally conductive wall; while the passageways 24
for flow of a gas stream containing reactants comprising one or
more organic compounds are illustrated to extend normal to the
viewing paper and are formed by spaces between exposed wall
surfaces of the reactor core tubes and side structures 12 defining
the of passageways 24.
The reactor core 11, and manifold structures 15, 21, 22, and 26 are
snugged or otherwise connected together and may be fit within a
housing (not shown) and/or have insulation surrounding these
components. Also, the annular space between the core, and separate
manifold structures can be packed or filled as at 29 with a seal to
minimize leakage of gases between the manifolds.
FIG. 3 illustrates a dual-flow reactor 30 having a reactor core 31
of monolithic construction. The monolithic core is approximately a
rectangular parallelepiped shape having two sets of entrance and
opposite side exit surfaces, each set spaced apart from and
substantially parallel with each other, and top and bottom outer
surfaces which are generally flat and approximately 90.degree. from
the entrance and exit surfaces. Structures 15 and 21 adjacent
opposite entrance surface (not shown) and exit surface 19 of
reactor core define spaced entrance and exit manifolds (not shown)
that communicate with one another via channels 13 formed in the
core. Further, structures 22 and 26 adjacent opposite exit surface
29 and entrance surface (not shown) of reactor core define spaced
entrance and exit manifolds (not shown) that communicate with one
another via channels 25 formed in the core. An inlet line 33 in
structure 15 is adapted to carry either an organic compound in an
oxygen-affording gas stream or another gas stream containing
reactants comprising one or more organic compounds to the entrance
manifold for flow through channels 13, and an outlet line 35 in
structure 21 is adapted to carry a residue of the oxygen-affording
gas stream or all remaining gas, unconsumed reactants, and
product-containing gas mixture from the exit manifold. Likewise,
inlet line 46 in structure 26 is adapted to carry either an
oxygen-affording gas stream or another gas stream containing
reactants comprising one or more organic compounds to the entrance
manifold for flow through channels 25, and an outlet line 44 in
structure 22 is adapted to carry a residue of the oxygen-containing
gas stream or all remaining gas, unconsumed reactants, and
product-containing gas mixture from the exit manifold. Channels 13
and channels 25 are disposed transverse to one another, so that the
respective inlet and outlet manifolds for oxygen-affording gas
stream and for the another gas stream containing reactants are
located alternately adjacent one another. The reactor core 31 and
manifold structures 15, 21, 22, and 26 are snugged or otherwise
connected together and may be fit within a housing (not shown)
and/or have insulation surrounding these components. Also, the
annular space between the top core, bottom structure, and separate
manifold structures can be packed or filled with a ceramic paste or
the like seal to minimize leakage of gases between the
manifolds.
FIG. 4 illustrates an enlarged cross section of a ceramic reactor
core 31 for dual-flow reactor 30 of FIG. 3. Channels 13,
specifically shown for a gas stream of an organic compound in an
oxygen-affording gas, are illustrated to extend in the plane of the
viewing paper and are formed by catalytic heat-transfer walls 51
comprising a gas-impervious material 53 supporting a suitable
catalyst 55 which together form a thermally conductive wall; while
the passageways 25 for flow of a gas stream containing reactants
comprising one or more organic compounds are illustrated to extend
normal to the viewing paper and are formed in the gas-impervious
material 53.
It will be appreciated that in dual-flow reactor 10 having an array
of reactor tubes 11, the passageways 24 and channels 13 are laid
out in a crosswise pattern so that the two gas streams flow
transverse to one another, and in dual-flow reactor 30 having a
monolithic core of reactor cells 31, the channels 25 and channels
13 are laid out in a crosswise pattern so that the two gas streams
flow transverse to one another. These cross flow arrangements allow
for direct and efficient manifolding of the opposite open ends of
the flow channels and/or passageways, and the manifolds can be
extended over almost the entire opposite entrance and exit surfaces
or edges of the cores.
Another embodiment of dual-flow reactor of the present invention
may be schematically represented as shown in FIG. 5 wherein the
side view and cross-section of the dual-flow reactor 50 shows
passageway 24 separated from channel 13 by catalytic heat-transfer
walls 51 comprising a gas-impervious material supporting a suitable
catalyst. Passageway 24 for flow of a gas stream is defined by
outer surface 14 of heat-transfer walls 51 and side structures 12.
The array of reactor tubes together is approximately a rectangular
parallelepiped shape. Tube channel 13 for flow of gases from
entrance surface to opposite exit surface defines a direction of
channel flow which is substantially parallel with the direction of
stream flow through passageway 24. Structures (not shown) adjacent
opposite entrance and exit surfaces of channel 13 define spaced
entrance manifold (not shown) and opposite exit manifold 20 (not
shown) that communicate with one another via channels 13. Further,
structures 22 and 26 define spaced entrance and exit manifolds (not
shown) that communicate with one another via passageways 24 formed
by spaces between outer surfaces of heat-transfer walls 51 and wall
structures 12. An inlet line is adapted to carry either an organic
compound in an oxygen-affording gas stream or another gas stream
containing reactants comprising one or more organic compounds to
the entrance manifold for flow through channels 13, and an outlet
line is adapted to carry a residue of the oxygen-affording gas
stream or all remaining gas, unconsumed reactants, and
product-containing gas mixture from the exit manifold. Likewise,
inlet line 44 in structure 22 is adapted to carry either an organic
compound in an oxygen-affording gas stream or another gas stream
containing reactants comprising one or more organic compounds to
the entrance manifold for flow through passageways 24, and an
outlet line 46 in structure 26 is adapted to carry a residue of the
oxygen-containing gas stream or all remaining gas, unconsumed
reactants, and product-containing gas mixture from the exit
manifold. Passageways 24 and channel 13 are disposed substantially
parallel to one another, so that the respective directions of gas
flow form inlet and outlet manifolds for an organic compound in an
oxygen-affording gas stream and for the another gas stream
containing reactants may be co-current or counter-current to one
another as desired.
The catalytic coupling of methane is, typically, carried out using
a feed that is essentially methane which can be pure methane or
methane containing various small amounts of other materials.
Natural gas, which is mainly methane, or other light hydrocarbon
mixtures which are readily available, inexpensive, are particularly
preferred feed materials for processes of this invention. The
natural gas can be either wellhead natural gas or processed natural
gas. Composition of processed natural gas varies with the needs of
the ultimate user. A typical processed natural gas composition
contains about 70 percent by weight of methane, about 10 percent by
weight of ethane, 10 percent to 15 percent of CO.sub.2, and the
balance is made up of smaller amounts of propane, butane and
nitrogen. The feed to the methane coupling reactor, preferably,
should not contain substantial amounts of C.sub.2 + hydrocarbons as
they are preferentially oxidatively dehydrogenated by the oxygen
present in the coupling process at the expense of methane and also
produce undesired water as a product. Natural gas containing
C.sub.2 + hydrocarbons can be used as a feed to the catalytic
methane coupling unit after first separating the C.sub.2 +
hydrocarbons, for example, by first passing the natural gas through
the demethanizer.
A large number of catalysts or agents are able to carry out methane
coupling and a considerable number are recorded in the public
literature. See, for example, U.S. Pat. No. 4,939,311 issued Jul.
3, 1990, in the name of Washecheck et al., U.S. Pat. No. 4,971,940
issued Nov. 20, 1990, in the name of Kaminsky et al., U.S. Pat. No.
5,024,908 issued Jun. 18, 1991, in the name of Karninsky et al.,
U.S. Pat. No. 5,059,740 issued Oct. 22, 1991, in the name of
Kaminsky et al., U.S. Pat. No. 5,196,634 issued Mar. 23, 1993, in
the name of Washecheck et al., and U.S. Pat. No. 5,198,596 issued
Mar. 30, 1993, in the name of Kaminsky et al. The specifications
and claims of each of these commonly assigned U.S. patents are
incorporated by reference herein.
Catalysts or agents useful in the methane coupling reaction are
generally heavy metal oxides, binary metal oxides and ternary metal
oxides. Preferably, the metals used are those whose oxides are not
volatile under the high temperature used in the methane coupling
reaction. Metal oxides and metal oxide systems such as lead oxide,
YBaZr oxide, SrLa oxide etc. may be used. It is preferable that the
catalyst or agent used is one which has a high activity,
conversion, and selectivity to C.sub.2 hydrocarbons, particularly
to ethylene, as can be understood by one skilled in the art.
Methane coupling is carried out over the catalyst or agent in the
presence of an oxygen-affording gas such as air, oxygen-enriched
air and oxygen, preferably oxygen, at pressures, temperatures and
space velocities that are well known to those skilled in the art.
Generally, the oxygen to methane ratio used is less than 1:1 so
that the oxygen is completely converted in the coupling reaction
and unreacted methane recycled to the methane coupling feed after
separation of the methane coupling products. The product of methane
coupling is largely the C.sub.2 hydrocarbons, ethane and ethylene,
with ethylene the most desired product. However, substantial
amounts of carbon oxides and water as well as smaller amounts of
C.sub.3 + hydrocarbons can be formed as can be understood by one
skilled in the art.
One or more zones of the dual-flow reactor can contain a fixed bed,
a moving bed, or a fluidized bed of particulate solids although a
fluidized bed reactor may be preferred from the point of view of
heat transfer. The partial oxidation catalyst or agent is, in a
favored embodiment, adhered to the walls in the form of a skin on
the reactor tube to facilitate transport of heat across the reactor
wall. The exothermic methane coupling process and the endothermic
hydrocarbon cracking process are carried out in the same reactor
separated by a thermally conducting wall between the reaction
zones. Preferably, a majority of the heat required in the
endothermic cracking process is supplied by the heat evolved in the
methane coupling process. More preferably, over 70% of the heat is
supplied by methane coupling. The heat supplied by methane coupling
is produced less pollutively than by burning, for example, methane
with air as the amount of NO.sub.x is reduced to almost zero.
Instead of introducing feed air to the liquid air plant at ambient
temperature, advantage can be taken of the existing refrigeration
unit present in the usual olefins plant. In this embodiment, feed
air is first cooled in stages in the propylene refrigeration unit
and then further cooled in the ethylene refrigeration unit. It may
be fed then to the liquid air plant at temperatures down to
-150.degree. F. at 16 psia.
Hydrocarbon cracking is carried out using a feed which is ethane,
propane or a hydrocarbon liquid ranging in boiling point from light
straight run gasoline through gas oil. Ethane, propane or mixtures
thereof is the preferred feed to a hydrocarbon cracking unit.
Generally, hydrocarbon cracking is carried out thermally in the
presence of dilution stem in large cracking furnaces which are
heated by burning at least in part methane and other waste gases
from the olefins process resulting in large amounts of NO.sub.x
pollutants. The hydrocarbon cracking process is very endothermic
and requires large quantities of heat per pound of product.
However, newer methods of processing hydrocarbons utilizes at least
to some extent catalytic processes which are better able to be
tuned to produce a particular product slate. The amount of stem
used per pound of feed in the thermal process depends to some
extent on the feed used and the product slate desired. Generally,
stem pressures are in the range of about 30 lb/in.sup.2 to about 80
lb/in.sup.2, and amounts of stem used are in the range of about 0.2
lb of stem per lb of feed to 0.7 lb of stem per lb of feed. The
temperature, pressure and space velocity ranges used in thermal
hydrocarbon cracking processes to some extent depend upon the feed
used and the product slate desired, which are well known as may be
appreciated by one skilled in the art.
The following Examples will serve to illustrate certain specific
embodiments of the herein disclosed invention. These Examples
should not, however, be construed as limiting the scope of the
novel invention as there are many variations which may be made
thereon without departing from the spirit of the disclosed
invention, as those of skill in the art will recognize.
EXAMPLES
In the following Examples catalytic heat-transfer walls which have
both gas-impervious materials and suitable catalysts allowing
oxidative coupling of methane into higher hydrocarbons were
prepared as follows.
Example 1
1% Sr/La.sub.2 O.sub.3 coated Ni Tube
A pure nickel tube (3/8" O.D., 0.035" wall, 1.25" long) was
roughened using sandpaper and then cleaned using acetone. A gray
homogenized slurry of ceramic adhesive was prepared by first mixing
8.0 g of a commercial MgO/Al.sub.2 O.sub.3 powder (CERAMABOND.TM.
571 from Aremco Products, Inc., Ossiing, N.Y.) with 5.33 g of
liquid sodium silicate in a vial. The roughened tube was dipped
into the gray homogenized slurry so that the entire inside and
outside surface of the tube was coated. The tube was allowed to air
dry overnight and then cured by heating in air according to the
following temperature program: Heat at 5.degree. C./min to
93.degree. C., hold for 2 hours, heat at 2 C./min to 371.degree.
C., hold for 1 hour, cool to room temperature. The coated tube was
then subjected to oxidative coupling conditions at temperatures
from 600.degree. C. to 850.degree. C. This caused the coating to
become more of an off white, tan color.
A catalyst, identified as 1% Sr/La.sub.2 O.sub.3, was prepared by
dissolving Sr(NO.sub.3).sub.2, (0.48579 g, 0.002295 moles) into 20
mL of deionized water and to this solution La.sub.2 O.sub.3 (20.0
g, 0.06138 moles) powder was added while mixing to form a
paste.
The coated tube was then rolled in this paste such that a certain
amount of the paste adhered to the tube. The coated tube was then
calcination according to the following temperature program: Heat at
2.degree. C./min to 400.degree. C., hold for 1 hour, heat at
2.degree. C./min to 850.degree. C., hold for 8 hours, the cool to
room temperature. The off white Sr/La.sub.2 O.sub.3 was adhered to
the walls of the tube after this treatment.
Example 2
1% Sr/La.sub.2 O.sub.3 coated Ni Tube
Preparation of catalytic heat-transfer walls according to Example 1
was repeated in several modifications as described in this example.
Both a nickel tube and a Incoloy-600 tube were coated with a
ceramic adhesive in a manner similar to that described in Example
1. A Sr/La.sub.2 O.sub.3 solution was prepared by dissolving
Sr(NO.sub.3).sub.2 (0.024 g, 1.15.times.10-4 moles) and
La(NO.sub.3).sub.3 .cndot.6H.sub.2 O (5.0 g, 0.0115 moles) in 10 mL
of acetone mixed with 3 mL of deionized water. The nitrates were
dissolved by gently heating the mixture which also evaporated some
of the acetone and caused the viscosity of the liquid to increase.
The coated tubes which had been cured to 371.degree. C. were dipped
into this solution and then dried at 120.degree. C. in a vacuum
oven for 30 minutes. The tubes were again dipped into the solution
and dried to increase the coating thickness. The coated tubes were
then calcined to 850.degree. C. for 8 hours.
Example 3
Y.sub.1 Ba.sub.2 Zr.sub.3 O.sub.y coated Ni Tube
A catalyst with nominal composition Y.sub.1 Ba.sub.2 Zr.sub.3
O.sub.y was prepared by heating Ba(OH).sub.2 .cndot.8H.sub.2 O (25
g, 0.0792 moles) in a 3-necked flask under a nitrogen purge until
it melted at temperatures form about 85.degree. C. to about
90.degree. C. Y(NO.sub.3).sub.2 .cndot.6H.sub.2 O and
ZrO(NO.sub.3).sub.2 .cndot.xH.sub.2 O were added to this melt with
stirring to form the desired solution. The resulting liquid was
allowed to cool and then was transferred as a solid to a
Y(ZrO.sub.2) crucible where it was calcined to 850.degree. C. for 8
hours. The calcined powder (1.54 g) was then mixed with 6.00 g of
MgO/Al.sub.2 O.sub.3 powder. To this mixture 6.06 g of liquid
sodium silicate was added and mixed to a paste consistency. A pure
nickel tube was coated with this mixture and followed by curing and
calcination as described in Example 1.
Example 4
Y.sub.1 Ba.sub.2 Zr.sub.3 Oy Coated Ni Tube
The Y.sub.1 Ba.sub.2 Zr.sub.3 O.sub.y catalyst describe in Example
3 (4.3 g) was ground to a fine powder and mixed with liquid sodium
silicate (3.6 g). The resulting paste was then used to coat another
pure nickel tube of the same size as described in Example 1. A
thick coating adhered to the tube which was then air dried and
cured as described in Example 1. The final calcination was done in
air at 850.degree. C. for 8 hours.
Example 5
Y.sub.1 Ba.sub.2 Zr.sub.3 O.sub.y coated Ni Tube
A ceramic adhesive was prepared by mixing MgO/Al.sub.2 O.sub.3
powder (6.0 g) with liquid sodium silicate (6.0 g) in air forming a
paste. A pure nickel tube was then dipped into this paste so that a
uniform coating covered the inside and outside of the tube. The
calcined Y.sub.1 Ba.sub.2 Zr.sub.3 O.sub.y (2.0 g of 60/80 powder)
was then sprinkled onto the wet coating and allowed to air dry. The
coated tube was then cured and calcined as described in Example
1.
Example 6 and Comparative Example A
Catalyst coated tubes were screened for catalytic activity using a
three zone electric tube furnace micro reactor. The 3/8" O.D.,
1.25" long coated tubes were placed into a 14 mm I.D. quartz
reactor tube. The coated tube replaced a conventional packed bed of
comparable catalyst. A quartz thermocouple well was placed up the
middle of the coated tube which was held in the middle of the
reactor tube with a quartz wool plug and a quartz deadman. The feed
was 30% CH.sub.4, 6% O.sub.2 and the balance N.sub.2. The results
for the 13702-125-1 Sr/La.sub.2 O.sub.3 coated Ni tube are shown in
Table 1. At 850.degree. C. at least 61% C.sub.2 + selectivity and
97% oxygen conversion was observed at 350 sccm of feed. Results
shown for Comparative Example A in Table 1 under heading
Conventional Packed Bed were obtained using 1% Sr/La2O3 by diluting
catalyst 39 to 1 with .alpha. Al.sub.2 O.sub.3 particles.
Example 7 and Comparative Example B
The screening for catalytic activity described for Example 6 and
Comparative Example A was repeated in these examples using Y.sub.1
Ba.sub.2 Zr.sub.3 O.sub.y catalyst. Results are shown in Table 2
below. For temperatures at 850.degree. C. and feed flow rate of 152
sccm, total C.sub.2 + selectivity was 54% at 95.6% Oxygen
conversion.
TABLE 1 ______________________________________ OXIDATIVE COUPLING
OF METHANE OVER 1% Sr/La.sub.2 O.sub.3 Conventional Catalytic Heat-
Packed Bed Transfer Wall ______________________________________
Temp, .degree.C. 850 843 GHSV, hr.sup.-1 255,000 298,800 Conversion
of mole % mole % Oxygen 100 95 Methane 22.5 23.3 Selectivity to
mole % mole % C.sub.2 H.sub.4 30.57 31.59 C.sub.2 H.sub.6 25.32
26.57 C.sub.2 H.sub.2 0.62 0.0 C.sub.3 H.sub.8 0.96 1.2 C.sub.3
H.sub.6 2.36 2.29 Methyl Acetlyene 0.14 0.06 Allene 0.09 0.05
C.sub.4 H.sub.6 0.35 0.75 CO 6.4 8.35 CO.sub.2 33.18 29.2 TOTAL TO
C.sub.2+ 60 62 ______________________________________
TABLE 2 ______________________________________ OXIDATIVE COUPLING
OF METHANE OVER Y.sub.1 Ba.sub.2 Zr.sub.3 O.sub.y Conventional
Catalytic Heat- Packed Bed Transfer Wall
______________________________________ Temp, .degree.C. 850 850
GHSV, hr.sup.-1 47,900 90,600 Conversion of mole % mole % Oxygen
100 95.6 Methane 25.3 19.4 Selectivity to mole % mole % C.sub.2
H.sub.4 38.88 33.09 C.sub.2 H.sub.6 23.90 16.84 C.sub.2 H.sub.2
0.86 0.64 C.sub.3 H.sub.8 0.71 0.0 C.sub.3 H.sub.6 2.82 3.04 Methyl
Acetlyene 0.22 0.3 Allene 0.13 0.15 C.sub.4 H.sub.6 0.0 0.57 CO
4.21 8.96 CO.sub.2 27.37 36.42 TOTAL TO C.sub.2+ 68 54
______________________________________
* * * * *